Other Connections

Falkayn saved Merseia which became the main enemy of the Terran Empire, and thus of Dominic Flandry, although some Merseians had settled peacefully on Dennitza, the home planet of Flandry's fiancee, Kossara Vymezal. Flandry's main personal enemy was not a Merseian but a Chereionite who worked for Merseia but for his ends, not theirs.

Since van Rijn's first trader team comprised Falkayn (Hermetian human), Adzel (Wodenite) and Chee Lan (Cynthian), it might follow from this that the main, although by no means the only, other intelligent species in the known space of the Technic History are:

Ythrians;
Wodenites;
Cynthians;
Merseians;
Chereionites, represented by their single survivor, Aycharaych, who (we think) dies during Flandry's bombardment of Chereion.

Also important are:

the gas-giant-dwelling Ymirites, whose domain, the "Dispersal," overlaps with human space;

the Baburites, also hydrogen-breathers, duped by a League cartel into playing a role that strikes a death blow to the League.